A jet pump is a mixed flow element, where a primary fluid having a high pressure ejects a secondary fluid having no or low pressure through the jet pump, and where the jet pump outputs a mixed fluid having an intermediate pressure. The most typical ejector is a Venturi ejector, where a body of the Venturi ejector is a circular pipe having an expanding cavity (namely a mixing chamber) at a front end of the circular pipe. An inlet of the secondary fluid is arranged at a side of the mixing chamber, and a nozzle connected with an inlet of the primary fluid is arranged in the mixing chamber. An outlet of the nozzle faces a mixing-output duct having a small diameter. The mixing-output duct is connected with an outlet of a contracting portion of the mixing chamber.
The Venturi ejector allows the primary fluid (namely working fluid) to entrain the ejected secondary fluid in the mixing chamber and enter into the mixing-output duct through the nozzle, which mixes the primary fluid and the secondary fluid in the circular pipe, controls heat and mass transfer and average pressure, and outputs the mixed fluid at an end of the circular pipe. Thus, delivery of the mixed fluid of the high pressure primary fluid entraining the low pressure secondary fluid is achieved.
Structure of the ejector with a single pipe has been largely unchanged. The ejector has a simple structure and reliable performance, but the ejector has the following defect:
To fully mix the primary fluid (the working fluid) and the secondary fluid (the ejected fluid), a long mixing duct (or a mixing-diffusion duct) is used. However, because the typical ejector is heavy and large, it is not useful in conditions that demand a light and small sized ejector. If the jet pump has the single pipe with a large diameter and large flow rate to spray the fluid and suck up the gas, the jet pump needs to have the mixing duct with a large diameter, and needs to have a jet flow of a large-diameter beam primary fluid. Because a jet flow of the primary fluid is in a center of the mixing chamber, the secondary fluid is entrained around the jet flow beam of the primary fluid, and as diameter of the jet flow of the primary fluid increases, a percent unit area contact rate and entrainment rate of the primary fluid and the secondary fluid reduces, namely ejecting coefficient of the primary fluid reduces, thus, effect of sucking up the gap (the secondary fluid is gap) reduces. To fully mix the primary fluid and the secondary fluid, and control heat transfer, mass transfer and average pressure, a length of the mixing duct (or the mixing-diffusion duct) increases, which results in reducing ejecting efficiency of the jet pump and increasing an axial size of the jet pump.
Pat No. ZL200920106414.7 provides an annular jet pump having a plurality of nozzles. The annular jet pump includes a plurality of small ejectors communicating with a central total pipe and circularly arranged in an external annular casing pipe, each of the small ejectors includes a nozzle, a throat pipe, and a diffusion pipe. The annular jet pump allows a high pressure fluid to eject a low pressure stratum fluid to a ground, and extract oil. The annular jet pump is a first-order parallel jet pump including a ring small round pipes in parallel and a central ball non-return valve. However, the annular jet pump structure is suited for extracting underground oil, but cannot be used as a large flow jet pump.